1. Field of the Invention
This invention relates generally to the field of multimedia systems. More particularly, the invention relates to a multimedia system capable of dynamically processing and combining different graphics and video using an appropriate resolution, aspect ratio, and interlaced/progressive scan type.
2. Description of the Related Art
Various prior art systems have been developed which render graphics on television displays. For example, as illustrated in FIG. 1a, set top boxes 100 from companies such as Web TV®, Replay TV® and Tivo® allow users to view various types of interactive graphical content 106 (e.g., Web pages, program menus, . . . etc), either displayed separately or overlayed on top of the standard broadcast video signal 105. The graphical content 106 may be transmitted along with the primary broadcast signal 105 (e.g., embedded within the signal's vertical blanking interval (“VBI”)), or over a separate data network such as the Internet (e.g., via a DSL modem, a cable modem or a standard telephone modem configured within the set top box 100, depending on the particular Internet service subscribed to by the end user).
One problem which exists with current systems, however, is that graphics designed for one type of display device may not be rendered properly on a different type of display device. For example, as illustrated in FIG. 1b, a graphical bitmap 115 designed to fit perfectly within a National TV Standards Committee (“NTSC”) television screen will have a resolution of less than 525 lines. The resolution of the bitmap image 115 is typically less than the maximum defined NTSC resolution of 525 lines (e.g., 420 lines) due to overscanning which occurs in standard television sets (i.e., some of the transmitted image is not viewable because the electron gun within the television scans slightly above and below the viewable portion of the picture tube).
When the same graphical bitmap 115 is displayed on a television 120 designed to render a Phase Alternating Line (“PAL”) signal, however, the image will no longer occupy the area which it was meant to occupy (e.g., the entire area in the example shown in FIG. 1b). Rather, because PAL provides a resolution 625 lines, an unsightly border 116 will surround the graphical bitmap 115. Similarly, when the graphical bitmap 115 is displayed on a high definition television (“HDTV”) 120, capable of rendering images at 1080 interlaced lines at an aspect ratio of 16:9, an even larger, asymmetrical border 117 will be produced.
Accordingly, what is needed is a system and method which will properly display graphics and video, regardless of the resolution and aspect ratio of the display device. What is also needed is a system and method which will convert, combine and render different graphics and video images for proper display on the display device. What is also needed is a system and method which will work with both interlaced and progressive display devices.